1. Proton = + charge Neutron = neutral charge Electron = - charge

2. Ions Ions are atoms that have lost or gained one or more electrons giving them a positive or negative charge!

3. For example: Na (Sodium), has originally 11 electrons but when an electron is lost it becomes a postive ion. Na + If an ion looses an election it has a positive charge. If an ion gains an electron it has a negative charge.

4. What causes an atom to become an ion? When an atom loses or gains one or more electrons it acquires a net electrical charge called an ion. The net charge of an ion is found by subtracting the number of electrons from the number of protons Charge of Ion = number of protons – number of electrons

5. A neutral magnesium atom (atomic number=12) has 12 protons/electrons. If it loses 2 electrons it becomes an ion with a charge of 2+. Number of protons 12 Number of electrons - 10 Charge of Ion 2+

6. 19. Cu²+ 20. F- 29 9 Ion Protons Electrons 27 10

7. Isotopes Isotopes are atoms that have the same number of protons but different numbers of neutrons Most elements in the first two rows of the periodic table have at least 2 isotopes with one being more common than the other In nature, elements are almost always found as a mixture of isotopes Hmm

8. For example, the most common isotope of hydrogen has no neutrons at all There's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons. Neutron Proton Isotopes of Hydrogen Most common isotope

9. To identify an isotope more specifically, chemists add a number after the elements name. ex. Carbon-11 Carbon-12 Carbon-14 This number is called the isotope’s mass number and is the sum of the isotope’s number of protons and neutrons. For example, an atom with 17 protons and 20 neutrons has a mass number of 37.

10. Q. What is the mass of the Nitrogen isotope with 7 protons and 12 neutrons? A. Nitrogen-19

11. iodine-128 potassium-40 53 19 53 19 75 21 Atom Protons Neutrons Electrons Examples

12. To name an isotope using chemical symbols  simply place the atom’s mass number to the upper left of the element symbol. For example 37 Cl. #neutrons = atomic mass – atomic number 37 – 17 = 20 neutrons

13. How many protons, neutrons, and electrons are present? 56 26 STEP 1: The atomic number in the lower left corner = 26 protons. The difference between the mass number and the atomic number is 56 – 26 = 30. There are 30 neutrons. STEP 2: The charge on the ion, 2+ shows us that there are 2 more protons than electrons, indicating that there are 24 electrons. Fe 2+

14. Isotope Symbols 141 56 Mass number (M) Atomic number (Z) Charge Ba 2+

15. Number of protons = Z Number of neutrons = M – Z charge = Z– Number of electrons